A manufacturing execution system (hereinafter “MES”) tracks material (e.g., substrate lots and carriers) and its associated process flow (e.g., sequence of process steps) within an electronic device fabrication facility (hereinafter “Fab”). The MES also tracks the state of the resources in the Fab that are used in the processing of substrate lots or carriers (e.g., the state of tools, storage devices, transport equipment, robots, etc.). Each time processing of the substrates in a lot or carrier completes a certain processing step (e.g., processing at a particular tool), the MES is informed of this status and determines the next destination for the carrier based on a set of operating rules that is typically Fab specific. For example, the MES may interact with a dispatcher or a scheduler to determine a tool that can perform the next process step on the substrates in the carrier, or a storage location if no such tool is available. Once a destination of the carrier has been determined, the MES sends a request to material control software (hereinafter “MCS”) to move the carrier from its current location to the determined destination. The MES also sends information and commands to the tools of the Fab, instructing each tool how to process the lot of substrates in each carrier that is delivered to the tool. This process continues until the lot of substrates in the carrier has completed all steps in its process flow.
The MCS is responsible for the transportation of carriers, using automated or manual delivery systems, from one location to the next within the Fab. This software tracks the carriers that are within the domain of the MCS (e.g., in storage stockers, on delivery vehicles, etc.) and determines the best route, based on the state of delivery systems, that should be used to transport each carrier from one location to the next. The MCS acts on (e.g., executes) carrier move requests from the MES, and informs the MES when these requests have been completed.
The majority of Fabs designed to manufacture electronic devices on 200 and/or 300 mm sized semiconductor wafers currently operate with twenty-five substrate lots, (e.g., the carriers used to transport the substrates to the tools of a Fab typically will store twenty-five substrates). Thus, the various equipment (e.g., process tools, metrology tools, etc. used to process the substrates and material handling equipment used to transport and store the carriers) and software (MES, MCS, schedulers/dispatcher, cell controllers, etc.) suppliers typically design their products to achieve optimal throughput under these conditions (e.g., approximately twenty-five substrates in a carrier).
However, the majority of the substrate processing and metrology tools in conventional Fabs process substrates one at a time, even though the substrates are transported and delivered in carriers as a lot of twenty-five substrates. Accordingly, a substrate transported in a carrier has to wait until all the other substrates transported in the carrier are processed at a tool before the substrate can be transported to the next process step. This waiting time leads to a longer cycle time for each substrate processed in a Fab and a higher work-in-progress (WIP) inventory in the Fab. The above problem may further compound with longer substrate processing times when performing individual process steps at process or metrology tools.
Systems and methods that reduce the extended cycle times of prior art systems are desirable.